1. Field of the Invention
This invention relates to a tape cassette suitable for use in an 8 mm-video tape recorder or the like for recording and/or reproducing audio and video signals.
2. Description of the Prior Art
For a conventional magnetic tape end detection used in a reel-to-reel type tape cassette, the ends of respective transparent leader and trailer tapes are secured to a supply reel and a takeup reel accomodated in parallel in the cassette. A magnetic tape is interposed between the leader and trailer tapes and wound on either the supply reel or the takeup reel. Then, a light is reflected on or transmitted through the leader or trailer tape and reflected or transmitted light is detected, whereby the beginning or the end of the tape is detected.
A tape cassette for use in recording and/or reproducing a video signal employing such transmissive light is disclosed in Official Gazette of Japanese Utility Model Registration Publication No. 55-40618. The tape cassette shown in this document has an opening through the bottom part at a position near the front surface of the cassette between the supply and takeup reels accomodated in parallel in the cassette for receiving a light projecting section and light receiving windows formed through both side walls of the cassette for transmitting therethrough the light from a light projecting element of the light projecting section inserted in the opening. When the leader tape or the trailer tape is facing the light receiving windows, the light from the light emitting element is incident on a light receiving surface of a light receiving element disposed in the vicinity of the light receiving window, whereas the light from the light emitting element is interrupted by the magnetic tape when the magnetic tape is present at the light receiving window, thereby allowing for detection of the beginning or the end of the magnetic tape.
In the above-mentioned tape cassette construction, if the cassette accomodating a metal tape, particularly a vapor deposition tape or the like which does not use a binder as a metal thin film, is left unused for a long time, dust and gas in the atmospheric air which may cause damage to the tape surface can readily enter into the cassette through the light receiving windows formed through the side walls and the light projecting section inserting opening, whereby dust not only gets on the magnetic tape surface but also rust may appear on the tape, particularly the vapor deposition tape.
Naturally, the above-mentioned conventional tape cassette is provided with a lid for closing the front opening portion of the cassette to protect the exposed tape and prevent dust from getting on the tape for preserving the cassete when it is not used for a long time. This lid is designed to also close the light receiving windows formed through the side walls. However, such construction cannot completely prevent rust from appearing on the tape.